Most oil and gas wells require stimulation to enhance hydrocarbon flow to make or keep them economically viable. The servicing of oil and gas wells to stimulate production requires the pumping of fluids into the well under high pressure. The fluids are generally corrosive and/or abrasive because they are laden with corrosive acids and/or abrasive proppants, such as sharp sand or bauxite.
In order to protect components that make up the wellhead, such as the valves, tubing hanger, casing hanger, casing head and/or blowout preventer equipment, wellhead isolation equipment, such as a wellhead isolation tool, a casing saver or a blowout preventer protector is used during well fracturing and well stimulation procedures. The wellhead isolation equipment may include a “blast joint” that is connected to a production tubing in the well used as a “dead string” to monitor downhole pressure during well stimulation and to flow back stimulation fluids after the well stimulation is complete, or as an additional fluid path for delivering high pressure stimulation fluids into the well.
As shown schematically in FIG. 1, a wellhead isolation tool 10 includes a sealing assembly 12, e.g. a “cup tool” or a high pressure fluid seal for a blowout preventer protector that seals off in a tubing spool above a bit guide. A blowout preventer protector equipped with a cup tool is described in U.S. Patent Application Publication 2003/0192698 (Dallas) entitled BLOWOUT PREVENTER PROTECTOR AND METHOD OF USING SAME which was published on Oct. 16, 2003 and which is hereby incorporated by reference. An example of a sealing assembly that seals off above a bit guide is described in U.S. Patent Application Publication 2003/0221838 (Dallas) entitled WELL STIMULATION TOOL AND METHOD OF USING SAME which was published on Dec. 4, 2003 and which is hereby incorporated by reference.
The wellhead isolation tool 10 further includes a blast joint 20 that has a threaded lower end 22 for connection to a threaded top end 32 of a tubing string 30 supported by slips 34 on a wellhead 40. The wellhead isolation tool 10 is lowered by a rig (not shown) into contact with the threaded top end 32 of the tubing string 30 and then the entire wellhead isolation tool 10 is rotated to connect the blast joint to the tubing string. As can be appreciated by those of ordinary skill in the art, connecting the blast joint to the tubing string in this way can be challenging. Precise control of the tool 10 must be exercised to ensure proper engagement of the threaded ends of the blast joint and the tubing string. If the tool 10 is a bit too high, the threads will not engage. If, however, the tool 10 is a bit too low the tool 10 will tilt as it is rotated and there is a real danger of cross-threading. The difficulty of connecting wellhead isolation equipment using this prior-art technique can therefore result in unwanted delays and/or equipment damage.
Accordingly, there remains a need for an improved apparatus and method for connecting a blast joint to a tubing string.